| 摘要 |
A switching power supply device that uses a SJ-MISFIT reduces a surge in voltage caused by the oscillation of drain current. The switching power supply device of the present invention, which is switched by a switching element that is a MOSFET having a super junction structure, includes an oscillation reduction diode connected in anti-parallel to the switching element, wherein when a characteristic curve of output capacitance Coss of the switching element relative to a drain-to-source voltage VDS is approximated by a first line, second line and third line corresponding to lines A, B and C shown in FIG. 2, junction capacitance CD2 of the oscillation reduction diode at a point b where a characteristic curve of the junction capacitance CD2 of the oscillation reduction diode and the second line cross each other is 40% or more of the output capacitance Coss of the switching element at a point a where the first and second lines cross each other.
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